Globally, Nigeria has the 2nd largest number of: a) people living with HIV, b) new HIV infections, and c) pregnant women living with HIV. In 2013 only 17.1% of women of childbearing age 15-49 years received an HIV test (preceding 12-months) and only 27% of the estimated 190,000 HIV-infected pregnant women in Nigeria who delivered babies received antiretroviral therapy for prevention of mother-to-child HIV transmission (PMTCT), compared to 68% of pregnant women receiving ART overall in sub-Saharan Africa (SSA). Nigeria accounts for 25% of new childhood HIV infections among the 21 priority countries (estimated 51,000 new infections). Roughly 49% of HIV-infected pregnant women in SSA are lost to follow up between registration in antenatal care and delivery, and 45% of infants are lost after HIV testing. Nigeria has high loss to follow-up (15%-56%) among HIV-infected women and children. In 2014, we demonstrated that the Healthy Beginning Initiative (HBI), a congregation-based intervention delivered by church-based health teams, was more effective in increasing HIV testing among pregnant women compared to a clinic-based approach. HBI uses church organized baby showers to engage and identify women early in pregnancy, combines educational intervention with integrated, on-site laboratory testing designed to reduce stigma associated with HIV-only testing. Baby receptions facilitate post-delivery follow-up and linkage to care. HBI addresses several barriers to HIV testing: perception of low risk to infection (education), access to testing and treatment, and cost and stigma (on-site, free, integrated testing). At least one faith-based institution is in each community, presenting a unique opportunity to evaluate the effectiveness of iSTAR, an integrated community and clinic based intervention that is designed to test, link, engage and sustain HIV-infected women in care. We propose a cluster randomized comparative effectiveness trial of iSTAR versus a clinic-based approach (CG). We will assess linkage, engagement, retention and viral suppression among 400 HIV-infected women. Based on the EPIS framework, we will use social network intervention methods to facilitate implementation and also assess implementation leadership and context. Fifty churches in south-south Nigeria will be randomly assigned (1:1) to iSTAR or CG. The iSTAR intervention provides: confidential, onsite integrated laboratory testing during baby showers; a network of church-based health advisors; clinic based teams trained in motivational interviewing; quality improvement skills to engage and support HIV-infected women; and integrated case management to reduce loss to follow-up. Primary outcomes are difference in linkage and engagement rates between iSTAR and CG. Secondary outcomes are difference in retention and viral suppression rate. This proposal is a collaboration among University of Nigeria (PEPFAR-funded partner in Nigeria [training and local project oversight]; University of Southern California (network analysis); UC San Diego (implementation science); UIC Chicago (assessment of sustainment); Nevada State College (statistical analyses and mediation/moderation analysis), and University of Nevada, Las Vegas (overall oversight of program implementation and evaluation).